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Viewing changes to src/golang.org/x/net/icmp/ipv4.go

  • Committer: Nicholas Skaggs
  • Date: 2016-10-24 20:56:05 UTC
  • Revision ID: nicholas.skaggs@canonical.com-20161024205605-z8lta0uvuhtxwzwl
Initi with beta15

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src/golang.org/x/net/icmp/ipv4.go
 
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// Copyright 2014 The Go Authors. All rights reserved.
 
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// Use of this source code is governed by a BSD-style
 
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// license that can be found in the LICENSE file.
 
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package icmp
 
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import (
 
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        "net"
 
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        "runtime"
 
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        "unsafe"
 
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        "golang.org/x/net/ipv4"
 
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)
 
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// See http://www.freebsd.org/doc/en/books/porters-handbook/freebsd-versions.html.
 
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var freebsdVersion uint32
 
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// ParseIPv4Header parses b as an IPv4 header of ICMP error message
 
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// invoking packet, which is contained in ICMP error message.
 
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func ParseIPv4Header(b []byte) (*ipv4.Header, error) {
 
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        if len(b) < ipv4.HeaderLen {
 
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                return nil, errHeaderTooShort
 
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        }
 
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        hdrlen := int(b[0]&0x0f) << 2
 
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        if hdrlen > len(b) {
 
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                return nil, errBufferTooShort
 
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        }
 
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        h := &ipv4.Header{
 
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                Version:  int(b[0] >> 4),
 
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                Len:      hdrlen,
 
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                TOS:      int(b[1]),
 
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                ID:       int(b[4])<<8 | int(b[5]),
 
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                FragOff:  int(b[6])<<8 | int(b[7]),
 
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                TTL:      int(b[8]),
 
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                Protocol: int(b[9]),
 
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                Checksum: int(b[10])<<8 | int(b[11]),
 
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                Src:      net.IPv4(b[12], b[13], b[14], b[15]),
 
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                Dst:      net.IPv4(b[16], b[17], b[18], b[19]),
 
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        }
 
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        switch runtime.GOOS {
 
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        case "darwin":
 
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                // TODO(mikio): fix potential misaligned memory access
 
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                h.TotalLen = int(*(*uint16)(unsafe.Pointer(&b[2:3][0])))
 
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        case "freebsd":
 
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                if freebsdVersion >= 1000000 {
 
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                        h.TotalLen = int(b[2])<<8 | int(b[3])
 
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                } else {
 
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                        // TODO(mikio): fix potential misaligned memory access
 
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                        h.TotalLen = int(*(*uint16)(unsafe.Pointer(&b[2:3][0])))
 
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                }
 
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        default:
 
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                h.TotalLen = int(b[2])<<8 | int(b[3])
 
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        }
 
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        h.Flags = ipv4.HeaderFlags(h.FragOff&0xe000) >> 13
 
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        h.FragOff = h.FragOff & 0x1fff
 
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        if hdrlen-ipv4.HeaderLen > 0 {
 
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                h.Options = make([]byte, hdrlen-ipv4.HeaderLen)
 
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                copy(h.Options, b[ipv4.HeaderLen:])
 
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        }
 
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        return h, nil
 
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}